Investigation : Homocysteine
Specimen type : Plasma
Spec container : Fluoride (K EDTA) 
Volume required : 4 ml
Reference range : see below µmol/l
Turnaround : <10 days

Transport to laboratory on ice immediately - must be centrifuged within 1 hour. Fasting sample prefrerred. Contact Duty Biochemist for information.

Potassium EDTA specimens are also acceptable.

Reference range:Normal:<15µmol/L
Moderate hyperhomocysteinaemia: 16-30µmol/L
Intermediate hyperhomocysteinaemia:31-100µmol/L
Severe hyperhomocysteinaemia:>100µmol/L

Causes of an increased plasma homocysteine level
Causes of a decreased plasma homocysteine level
Delayed sample separation can artificially increase homocysteine levels.
Samples must be transported to the laboratory immediately and centrifuged within 1 hour.
Genetic factors
Homocystinuria, methylenetetrahydrofolate reductase (MTHFR) mutation 677C->T. Down's Syndrome
Lifestyle determinanants
SmokingVitamin intake (folate, cobalamin, B6, B12), exercise.
Clinical conditions
Folate deficiency, cobalamin deficiency, renal failure, hypothyroidism, cardiovascular disease, cerebral vascular accident, thrombophilia 
Anti-folates (methotrexate, anticonvulsants, trimethaprim), nitrous oxide anesthesia, L-Dopa, fibrates, cyclosporin.  
Physiological determinants

Other investigations to consider when plasma homocysteine levels are raised:

*Please contact duty biochemist for information.

# Used to reveal additional abnormalities of the homocysteine metabolism not detected by homocysteine concentration measurements. An elevated homocysteine level post methionine load must be taken into account in the general identification of patients bearing trans-sulphuration defects (e.g. vitamin B6 deficiency) or heterozygotes for cystathionine β-synthase (CBS) deficiency. Please contact duty biochemist for further information.

Additional information on Homocysteine and its clinical use can be found here: Homocysteine.


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